1. Field of the Invention
The present invention relates to, inter alia, an aligner for use in production/inspection devices for semiconductors, a wafer transferring device equipped with the aligner, and a semiconductor production device equipped with the water transferring device. More specifically, the present invention relates to a pre-aligner for centering a wafer or adjusting an orientation angle of a notch or the like formed on a peripheral edge of a wafer, a wafer transferring device equipped with the aligner, and a semiconductor production device equipped with the water transferring device.
2. Description of Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
In a semiconductor production device or the like, a pre-aligner is mainly used in combination with a wafer handling robot and configured to detect a specific cut-out portion formed on an external periphery of a wafer called “notch” or “orientation flat” with a detection sensor mounted on the pre-aligner while revolving the wafer transferred from the wafer handling robot and to align the wafer to a prescribed angular orientation based on the detected information. In a recent semiconductor production apparatus, the pre-aligner is installed together with a wafer handling robot within the so-called locally cleaned housing isolated by a box at a filtered downstream flow side. At the side of the housing, a cassette opener (called “POD opener” or “FOUP opener”) for opening/closing a cassette (e.g., FOUP) storing wafers is provided so that the cassette can be opened/closed with the cassette opener without introducing non-cleaned atmosphere existing outside the housing. While aligning the wafer in the cassette with the pre-aligner, the wafer handling robot transfers the aligned wafer to a processing device arranged adjacent to the housing. The processing device executes prescribed processing, such as, e.g., CVD, etching, or exposure. The wafer processed by the processing device is returned to the cassette again. In this case, the housing constitutes a transferring device called “front-end device.” Furthermore, other housings have been developed. In a housing, a plurality of cassette openers are provided at the side of the housing so that a wafer housing handling robot transfers a wafer while aligning it with the aligner among the plurality of cassettes above the plurality of cassette openers. This housing is a transferring device called “sorter” or the like. In any event, a pre-aligner has been widely used in semiconductor production devices to align a position and/or direction of a wafer.
In a conventional prealigner, holding of a wafer has been widely performed by a wafer vacuum absorption method. However, in accordance with the recently increased wafer diameter and design rule miniaturization, particles not only on a top surface of a wafer but also on a bottom surface of the wafer have become an issue. In a vacuum absorption system, contamination of a wafer bottom surface due to the contact of the absorption holding member is inevitable. Under the circumstance, a prealigner equipped with a gripping arm for holding an edge (external peripheral portion) of a wafer has been developed.
For similar reasons, also in a wafer handling robot, such edge gripping has become mainstream for a wafer holding portion for disposing and transferring a wafer called an “end effector,” and has been used in combination with an edge-holding type pre-aligner
In the case of using an edge-holding type pre-aligner and a wafer handling robot in a transferring device, it is required to deliver a wafer while keeping a predetermined mutual positional relationship to avoid mutual interference of the gripping arm of the pre-aligner and the end effector of the robot.
The positional relationship will be explained together with the movements of the pre-aligner and handling robot. When a wafer is transferred from the robot to the pre-aligner, the wafer is transferred to the pre-aligner with the notch portion taking an arbitrary position (i.e., in a state in which the notch position is unknown). At this time, to avoid the aforementioned mutual interference of the end effector and the gripping arm, the gripping arm is preliminarily rotated to a position where the gripping arm does not interfere with the end effector. In other words, at the time of transferring a wafer, the gripping arm and end effector should keep a prescribed positional relation.
The prealigner receiving a wafer detects the notch position with a notch detection sensor mounted on a part of the device while revolving the gripped wafer, and then rotates the wafer so that the notch takes a subscribed angular position required by a user. However, the position of the gripping arm after completion of the movement to the required notch angular position does not always satisfy a prescribed positional relation where the handing robot can transfer the wafer. Accordingly while keeping the position of the aligned wafer, it is required to move only the gripping arm to the prescribed position. Thus, in order to temporarily pass a wafer with the notch aligned and revolve the gripping arm to a prescribed position, it is required to equip a lifter for moving the wafer to the upper side of the gripping arm. The gripping of the wafer by the gripping arm is once released and the wafer is lifted up in a direction above the gripping arm. In this state, the gripping arm is moved (rotated) to a prescribed position, and then the wafer is returned to being disposed on the gripping arm by lowering the lifter. As a result, it becomes possible to insert the end effector of the handling robot, which enables the pick-up of the wafer by the wafer handling robot. Thus, the series of operations is completed.
In this lifter, only the edge portion of the wafer is a contact allowable portion. However, the gripping arm and the lifter commonly come into contact with the edge portion of the wafer, and the gripping arm takes an arbitrary position with respect to the notch angle aligned position. Therefore, at the time of moving the lifter up and down, the lifter may sometimes interfere with the gripping arm portion. That is, the gripping arm may sometimes be located within the lifting operation area of the notch angle positioned lifter.
As explained above, in order to transfer the wafer to the handling robot, it is required to move (rotate) the gripping arm to a previously determined prescribed position. Without avoiding this interference, the continuous operation as a transferring device cannot be performed.
An example for avoiding interference between a gripping arm and a lifter is disclosed in Japanese Unexamined Laid-open Patent Publication No. 2002-151577, A. As shown in FIGS. 11 and 12, the example disclosed in the aforementioned Patent Publication is provided with a plurality of divided substrate holding ledges which move up and down. A plurality of integrally formed substrate holding ledges arranged radially with respect to the rotational center constitute an up-and-down movable holding member. A plurality of up-and-down movable holding members are provided in an individual movable manner. That is, by forming plural groups of lifters, in the case where a certain group of lifters interferes with the gripping arm when the group of lifters is moved upwards, the interference is avoided by moving other groups of lifters.
However, in the device disclosed by the aforementioned Patent Publication, a plurality of divided substrate holding ledges are provided, and the holding ledges and other substrate holding ledges arranged radially with respect to the rotational center constitute an integrally formed up-and-down movable member. A plurality of up-and-down movable members are provided. Accordingly, as shown in FIG. 11, it is required to arrange the up and down movable members in the up-and-down direction, which increases the height of the device. Furthermore, each substrate holding ledge and the up-and-down movable holding member are separately constituted in an up-and-down movable manner. This requires individual driving power sources, resulting in complex structure and increased number of parts, which in turn increases the size of the device and the cost.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.